U.S. Pat. Nos. 3,716,569; 3,751,371; and 3,816,184 all assigned to Petrolite Corporation, disclose silicon-containing aminomethyl, or substituted aminomethyl phosphonic acids and derivatives as scale inhibitors and corrosion inhibitors. The compounds described in these inventions are prepared by first adding a mixture of water, phosphorous acid, and hydrochloric acid to an aminoalkyltrialkoxysilane, then heating this mixture and adding formaldehyde. The composition of this invention differs from that disclosed in the above Petrolite patents in the order of addition of the reagents and in the molar ratios of the reactants.
This invention relates to silicone reaction products that are obtained by reacting phosphorous acid, formaldehyde, and alkoxysilanes containing one or more aminoalkylene groups. These silicone products have been found to be useful to inhibit the gelation of aqueous silicate solutions and particularly aqueous glycol solutions containing alkali metal silicate.
The stabilization of aqueous silicate solutions with various siliconates has been reveiwed by E. P. Plueddenann in the book "Silane Coupling Agents" Plenum Publishing Co. 1982 pages 66-73.
In U.S. Pat. No. 4,367,154 there is disclosed the stabilization of aqueous glycol solutions with the reaction product of the reaction between 3-chloropropyl alkoxysilanes with dimethyl methyl phosphonate. The reaction products of this invention offer a significant cost advantage over these known stabilizers.
The Petrolite patents teach the use of equimolar amounts of formaldehyde and phosphorous acid for the preparation of their composition. In contrast, the composition of this invention is prepared by always using more formaldehyde than phosphorous acid, i.e., the molar ratio of formaldehyde to phosphorous acid is always greater than one. This excess of formaldehyde over phosphorous acid is believed to increase the possibility of methylene coupling between amines as illustrated below: EQU O.sub.1.5 Si--CH.sub.2 --CH.sub.2 --CH.sub.2 --NH--CH.sub.2 --CH.sub.2 --NH.sub.2 +H.sub.2 C(O).fwdarw.CH.sub.2 --NH--CH.sub.2 --CH.sub.2 --NH--CH.sub.2 --CH.sub.2 --CH.sub.2 --Si O.sub.1.5).sub.2 +H.sub.2 O.
This allows an increase in the size of the alkyl portion of the silane which results in more efficient silicate stabilization, by shielding the silicate moieties with the divalent silane.